Primer composition for polyolefin materials

ABSTRACT

Acid anhydride denatured chlorinated polyolefin (component A) which is composed of a copolymer of propylene and α-olefin wherein the chlorine contents is 15 to 24% by weight, denatured amount of acid anhydride is 0.6 to 2.0%, weight average molecular weight is 40000 to 120000, and acrylic denatured alkyd resin (component B) which is comprised of alkyd resin polymer part (b1) whose iodine value is 80 or more and oil length is 35 to 70, and acrylic resin polymer part (b2) whose glass-transition temperature is not less than 50° C. wherein the weight average molecular weight is 10000 to 100000, weight ratio of the alkyd part and acrylic part is in a range of from 25/75 to 75/25, are used in a range of from 80/20 to 20/80 (A/B).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a primer composition which is to beapplied to a polyolefin material.

2. Background Art

Polyolefin materials exhibit superior properties such as moldability andchemical resistance, and because it is relatively inexpensive, it iswidely used in plastic parts in industrial fields in recent years. Forexample, in an automobile, polyolefin is used for exterior parts such asbumpers or side panels, and it is also used for interior parts such asinstrument panels. In these cases, it is usually applied to improvedesign value and weatherability of the automobile. However, adhesion topolyolefin materials is insufficient, and coatings do not adhere topolyolefin materials, and easily peels off. Therefore, a primer isapplied on the polyolefin material to improve adherence before painting.In particular, the primer process is necessary for exterior parts ofautomobiles such as polyolefin bumpers.

As a primer for polyolefin materials for exterior parts for anautomobile which exhibits superior resistance to high-pressure washingand gasohol resistance, a primer composition consisting of chlorinatedpolypropylene having a specific structure and acrylic denaturedchlorinated polypropylene is disclosed in Japanese Unexamined PatentApplication Publication No. 31779/96. However, because the primercomposition mentioned above requires the molecular weight of acidanhydride denatured chlorinated polypropylene to be in a range of from30000 to 36000, a process for controlling the molecular weightdistribution is required in the producing process of acid anhydridedenatured chlorinated polypropylene. Therefore, the price of the primeris increased because the production cost of the primer is higher thanthat of a usual polyolefin. Therefore, an invention of a primer for apolyolefin material for exterior parts for an automobile which hascharacteristics of resistance to high-pressure washing and gasoholresistance without adding acid anhydride denatured chlorinatedpolypropylene which is controlled in a specific range of molecularweight, is required.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a primercomposition having sufficient adherence, resistance to high-pressurewashing, and gasohol resistance with respect to a polyolefin materialwithout adding acid anhydride denatured chlorinated polypropylene whichis controlled to be in a specific range of molecular weight.

To solve the problems described above, the inventors performed furtherresearch and have invented a method which exhibits sufficient adherence,resistance to high-pressure washing, and gasohol resistance withoutadding chlorinated polyolefin which is set in a specific range ofmolecular weight disclosed in Japanese Unexamined Patent ApplicationPublication No. 31779/96, and have completed the present invention.

In the primer composition for polyolefin materials of the presentinvention, sufficient adherence, resistance to high-pressure washing,and gasohol resistance are achieved by using acid anhydride denaturedchlorinated polypropylene and acrylic denatured alkyd resin together.That is to say, the characteristics of the primer composition forpolyolefin materials of the present invention are that the primercomposition comprises acid anhydride denatured chlorinated polyolefin(component A) and acrylic denatured alkyd resin (component B), theweight ratio of the component A and the component B is 80/20 to 20/80,and these components have characteristics as explained below.

Component A contains propylene for 50 to 90 mol %, and comprisespropylene-α-olefin copolymer in which at least one kind of α-olefinwhose carbon number is 2 or 4 to 6 is contained. Furthermore, thechlorine content is 15 to 24% by weight, the acid anhydride denaturedcontent is 0.6 to 2.0% by weight, and the weight average molecularweight is 40000 to 120000.

Component B comprises alkyd resin polymer part (b1) whose iodine valueis more than 80 and oil length is 35 to 70, and acrylic resin polymerpart (b2) whose glass-transition temperature is greater than 50° C.Furthermore, the weight average molecular weight is 10000 to 100000, andthe weight ratio of b1 and b2 is 25/75 to 75/25.

-   1. Components of the primer composition for polyolefin material

The primer composition for polyolefin materials of the present inventioncomprises component A: acid anhydride denatured chlorinated polyolefinresin and component B: acrylic denatured alkyd resin, as essentialcomponents. It is desirable that the weight ratio of component A and Bbe 80/20 to 20/80, and more desirably, 70/30 to 30/70. In the case inwhich the weight ratio of acid anhydride denatured chlorinatedpolyolefin is greater than 80%, resistance to high-pressure washing isreduced. Furthermore, in the case in which the weight ratio of acrylicdenatured alkyd resin is greater than 80%, the adherence to polyolefinmaterial is reduced and the coated primer composition may peel off fromthe material. Each component is explained further below.

Component A: Acid Anhydride Denatured Chlorinated Polyolefin

Acid anhydride denatured chlorinated polyolefins of the presentinvention comprise propylene-á-olefin copolymer which contains at leastone kind of á-olefin whose carbon number is 2 or 4 to 6 such asethylene, butene, or pentene, and contains propylene at 50 to 99 mol %.The chlorine content is 15 to 24%, the acid anhydride denatured contentis 0.6 to 2.0%, and the weight average molecular weight is 40000 to120000.

The ratio of copolymerization of the α-olefin in the propylene-α-olefincopolymer mentioned above is in a range of from 1 to 50 mol %, and moredesirably, in a range of from 5 to 30 mol %. In the case in which thisratio of copolymerization is below this range, crystallization isincreased and storage stability after a coating is prepared is reduced.On the other hand, in the case in which the ratio of copolymerization isabove this range, adherence and resistance to high-pressure washing arereduced. Weight average molecular weight of the propylene-α-olefincopolymer is in a range of from 40000 to 120000, more advantageously, ina range of from 50000 to 100000. In the case in which the weight averagemolecular weight is below this range, gasohol resistance is reduced, andin the case in which the weight average molecular weight is above therange, viscosity is increased, and this will hinder the coating process.

The chlorination of the propylene-α-olefin copolymer mentioned above canbe applied by a technique which is known. For example, chlorination canbe easily conducted by blowing chlorine gas into a chloroform solutionof the polyolefin at a high temperature. In the present invention, it isdesirable that the chlorinated ratio be in a range of from 15 to 24% byweight, and more desirably from 18 to 21% by weight. The chlorinatedratio is below the range mentioned above, storage stability after acoating is prepared is reduced, and seedings of the coating may form. Onthe other hand, in the case in which the chlorination ratio is above therange, the resistance to gasohol will be reduced.

Denaturation of acid anhydride is achieved, for example, by applyingaddition reaction of acid anhydride such as maleic anhydride or itaconicanhydride to the polyolefin described above. As this addition reactionmethod, a known method wherein acid anhydride is reacted with a radicalinitiator at high temperatures can be used. It is desirable that thereacted amount of acid anhydride be in a range of from 0.6 to 2.0% byweight, more desirably in a range of from 1.0 to 1.6% by weight. In thecase in which the reacted amount of acid anhydride is below the range,gasohol resistance tends to be reduced, and on the other hand, when thereacted amount of acid anhydride is above the range, moisture resistanceand storage stability after the coating is prepared is reduced.

As described above, chlorination process and acid anhydride additionreaction process at producing of the acid anhydride denaturedchlorination polyolefin of the present invention are techniques whichare already known, and either the chlorination process or the additionreaction process can be applied first.

Component B: Acrylic Denatured Alkyd Resin

Acrylic denatured alkyd resin used in the present invention comprisesalkyd resin having an oil length of 35 to 70 in which oils of more than80 by iodine value are used and denatured acrylic resin whoseglass-transition temperature is more than 50° C. Furthermore, the weightaverage molecular weight is 10000 to 100000, and the weight ratio of thealkyd resin polymer part and the acrylic resin polymer part is in arange of from 25/75 to 75/25.

Oil used in the alkyd resin is not limited if the iodine value isgreater than 80, such as castor oil, soybean oil, dehydrated castor oil,or linseed oil. Polybasic acid is also not particularly limited. Forexample, dicarboxylic acid such as orthophthalic acid, phthalicanhydride, tetrahydro orthophthalic acid, tetrahydro orthophthalicanhydride, or more than one kind of the acid anhydride, can be used.Furthermore, polyfunctional alcohol is also not limited. More than onekind of difunctional or higher alcohol such as pentaerythritol,glycerin, or neopentylglycol can be used.

The alkyd resin described above can be prepared by a known method. Forexample, under an atmosphere of inert gas, an alcoholysis reaction ofoils and polyfunctional alcohol is conducted with lithium hydroxidecatalyst at 200 to 250° C. Next, the alcoholysis reaction is completedby methanol tolerance, and after that, esterification is performed byconducting polyfunctional acid. Hydroxyl value of alkyd resin can becontrolled by adding polyfunctional alcohol if necessary, and in such acase, oil length is set in a range of from 35 to 70, more desirably,from 50 to 60.

Acrylic denaturation can be conducted by a known method by using thealkyd resin described above. For example, the alkyd resin is heated to120° C. under an atmosphere of an inert gas, a mixed solution of acrylicmonomer and peroxide is dropped at a constant interval, and this isheated for a specific time after adding the rest of the peroxide, andthus acrylic resin denaturation can be conducted.

Although the glass-transition temperature of the acrylic resin polymerpart is not particularly limited so long as it is above 50° C., it isadvantageous that the glass-transition temperature be above 60° C. Inthe case in which the glass-transition temperature is below 50° C.,resistance to high-pressure washing is reduced. As an acrylic monomer,acrylic ester monomer such as methyl acrylate, methyl methacrylate,butyl methacrylate, or 2-hydroxylethyl acrylate can be used, and alsostyrene, vinyl toluene, or α-methyl styrene can be used, and at leastone kind thereof is selected so that the glass-transition temperature isabove 50° C.

A suitable ratio of alkyd resin polymer part (b1) and acrylic resinpolymer part (b2) is in a range from 25/75 to 75/25 by weight, moresuitably from 40/60 to 60/40. In the case in which the weight ratio ofthe alkyd resin polymer part is less than 25%, gasohol resistancelowers, and on the other hand, the weight ratio of the acrylic resinpolymer part is less than 25%, resistance to high-pressure washing isreduced. The weight average molecular weight of the acrylic denaturedalkyd resin is in a range of from 10000 to 100000, and more desirablyfrom 15000 to 60000. In the case in which the weight average molecularweight is less than 10000, resistance to high-pressure washing andgasohol resistance are not exhibited because of low strength of thecoated film, and on the other hand, if the weight average molecularweight is more than 100000, viscosity is increased and atomization isreduced, and the smoothness of the coated film on polyolefin material isreduced. Furthermore, compatibility with acid anhydride denaturedchlorinated polyolefin is reduced and storage stability after thecoating is prepared is also reduced.

Other Components

The primer composition for polyolefins of the present inventioncomprises acid anhydride denatured chlorinated polyolefin and acrylicdenatured alkyd resin described above as essential components, and otherresin components such as acrylic resin, polyester resin, epoxy resin,acrylic denatured chlorinated polyolefin resin, cellulose resin,melamine resin, or block isocyanate resin can be added, if necessary. Inthese cases, 0 to 90 parts by weight of these resins can be added per100 parts weight of the total of the acid anhydride denaturedchlorinated polyolefin and acrylic denatured alkyd resin, and a coatingis prepared by adding mainly aromatic hydrocarbon solvents such astoluene or xylene, or ester solvents such as ethyl acetate or butylacetate, or ketone solvents such as methyl ethyl ketone or methylisobutyl ketone. These organic solvents are usually added at 200 to 500parts by weight per 100 parts by weight of the total of the acidanhydride denatured chlorinated polyolefin and acrylic denatured alkydresin.

Workability of the primer composition for polyolefins of the presentinvention can be improved by coloring and the primer composition of thepresent invention can also be used as an electrostatic coating by beingconductive with a pigment such as titanium oxide, carbonblack, orconductive carbonblack, or with an extender pigment such as talc, clay,or barium sulfate, or with various kinds of organic pigments. In thesecases, 0 to 100 parts by weight thereof are added per 100 parts ofweight of the total of acid anhydride denatured chlorinated polyolefinand acrylic denatured alkyd resin.

-   2. Coating by primer composition for polyolefin material

Although the method of coating a polyolefin material with the primercomposition for polyolefin material of the present invention is notlimited in particular, a typical spray coating is desirable. Dryingmethod of the primer is also not limited in particular, and it can bedried by using air-drying, a hot air drying furnace, or a far infraredradiation drying furnace at room temperature to 120° C. for 3 to 30minutes. The thickness of the coating film by the primer composition forpolyolefins of the present invention is not limited in particular, but 5to 15 μm is desirable. In the case in which the thickness is less than 5μm, basic characteristics cannot be exhibited, and it is actuallydifficult to obtain a continuous film. On the other hand, in the case inwhich the thickness is above 15 μm, the primer may be sagging.

Decoration of polyolefin material can be achieved by coating and dryingthe primer of the present invention and coating the top coat over thisprimer. This top coating process is not particularly limited, and 2 packsystem urethane coating, melamine coating, or lacquer coating can beapplied usually, and as a coating process, 2C1B specifications includingclear coat or mono coat 1C1B specifications is selected.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention is explained in detail by way of examples.

-   A. Preparing of polyolefin material having primer coating

EXAMPLE 1

7 parts by weight of acid anhydride denatured chlorinated polyolefin(A1, solid) shown in Table 1, 7 parts by weight of acrylic denaturedalkyd resin (B1, solid) shown in Table 2, 14 parts by weights of pigment(trade name: Titanium R-820, produced by Ishihara Sangyo Kaisha, Ltd.),and 72 parts by weight of toluene were mixed together, and thus theprimer composition for the polyolefin of Example 1 was prepared.

TABLE 1 Acid anhydride denatured chlorinated polyolefin A1 Mol ratio ofpropylene/ethylene 90/10 Content of maleic anhydride (%) 1.3 Weightaverage molecular weight 80000

TABLE 2 Acrylic denatured alkyd resin B1 B2 B3 B4 B5 B6 B7 B8Composition Dehydrated castor oil 50.5 50.5 50.5 50.5 50.5 50.5 50.550.5 of alkyd resin Phthalic anhydride 27.1 27.1 27.1 27.1 27.1 27.127.1 27.1 polymer part Pentaerythritol 14.5 14.5 14.5 14.5 14.5 14.514.5 14.5 Neopentylglycol  7.9  7.9  7.9  7.9  7.9  7.9  7.9  7.9 Total100 100 100 100 100 100 100 100 Composition Methyl methacrylate 61.061.0 61.0 69.9 61.0 61.0 51.0 61.0 of acrylic resin Styrene 20.0 20.020.0 20.0 20.0 20.0 20.0 20.0 polymer part n-Butyl acrylate 18.4 18.418.4 9.5 18.4 18.4 18.4 18.4 Methacrylic acid  0.6  0.6  0.6  0.6  0.6 0.6  0.6  0.6 Total 100 100 100 100 100 100 100 100 CharacteristicsAlkyd resin polymer 50/50 30/70 70/30 50/50 20/80 80/20 50/50 50/50 ofresin part/acrylic resin polymer part Oil length of alkyd resin  50  50 50  50  50  50  50  50 polymer part Glass-transition  60  60  60  80 60  60  40  60 temperature of acrylic resin polymer part Weight average30000  30000  30000  30000  30000  30000  30000  8000  molecular weight

Next, the primer composition for the polyolefins mentioned above whoseviscosity was processed to be 12 seconds/NO4F. C. by xylene was sprayedon a polyolefin material (trade name: SP-850, produced by IdemitsuPetrochemical Co., Ltd.) which was washed with hot water and dried, byspray gun to form a coating having a thickness of 10 μm. It is dried at80° C. for 10 minutes, to form a primer coating. Next, a base coating(trade name: R-301 silver metallic, produced by Nippon Bee Chemical Co.,Ltd.) was coated on the primer coating to form a thickness of 20 μm anda top clear coating (trade name: R-288 clear, produced by Nippon BeeChemical Co., Ltd.) was coated on the base coating to form a thicknessof 30 μm, and was dried at 80° C. for 30 minutes, to form a top coating.Thus, the polyolefin material coated with the primer composition ofExample 1 was prepared.

EXAMPLES 2 TO 6 AND COMPARATIVE EXAMPLES 1 TO 4

Compositions and kinds of the acid anhydride denatured chlorinatedpolyolefin and acrylic denatured alkyd resin in Example 1 were changedto conditions shown in Table 3 and 4, and thus primer compositions forpolyolefin of Example 2 to 6 and Comparative Examples 1 to 4 wereprepared and polyolefin materials coated with these primers wereprepared in the same way shown in Example 1.

TABLE 3 Examples 1 2 3 4 5 6 Acid anhydride denatured 7.0 10.5 3.5 10.53.5 7.0 chlorinated polyolefin A1 Acrylic denatured alkyd 7.0 3.5 10.5 —— — resin B1 Acrylic denatured alkyd — — — 3.5 — — resin B2 Acrylicdenatured alkyd — — — — 10.5 — resin B3 Acrylic denatured alkyd — — — —— 7.0 resin B4 Titanium oxide 14.0 14.0 14.0 14.0 14.0 14.0 Toluene 72.072.0 72.0 72.0 72.0 72.0 Total 100 100 100 100 100 100 Adherence 100/100100/100 100/100 100/100 100/100 100/100 Moisture resistance 100/100100/100 100/100 100/100 100/100 100/100 Gasohol resistance passingpassing passing passing passing passing Resistance to high-pressurepassing passing passing passing passing passing washing

TABLE 4 Comparative Examples 1 2 3 4 Acid anhydride denatured 12.6 1.47.0 7.0 chlorinated polyolefin A1 Acrylic denatured alkyd resin B5 1.4 —— — Acrylic denatured alkyd resin B6 — 12.6 — — Acrylic denatured alkydresin B7 — — 7.0 — Acrylic denatured alkyd resin B8 — — — 7.0 Titaniumoxide 14.0 14.0 14.0 14.0 Toluene 72.0 72.0 72.0 72.0 Total 100 100 100100 Adherence 100/100 80/100 100/100 100/100 Moisture resistance 100/100 0/100 100/100 100/100 Gasohol resistance passing 5 minutes passingpassing Resistance to high-pressure 4 mm 9 mm 1 mm 4 mm washing

-   B. Performance evaluation of primer coatings

The inventors evaluated the coating performance of the polyolefinmaterials coated with the primer compositions of each of the Examplesand the Comparative Examples, and the results are shown in Tables 3 and4.

Methods of evaluation

-   1. Cross-cut adhesion test

The coated polyolefin materials obtained above were cut to form slashesby a cutter knife until the blade reached to the material under thecoatings. Eleven slashes were made in the longitudinal direction andeleven slashes were made in the transverse direction at width of 2 mm,yielding 100 tessellated pieces. Peeling tests were performed byapplying and peeling off Cellotape (registered trade mark) on thepieces. Remaining pieces were counted after peeling off the Cellotape.

-   2. Moisture resistance

The polyolefin materials were put in an atmosphere of 50° C., humidity98%, for 240 hours and the peeling test described above was performed.

-   3. Gasohol resistance

The polyolefin materials were cut to have dimensions of 3 cm by 3 cm,and were put into a gasohol prepared by mixing commercial regulargasoline and ethanol at a ratio of 90:10 by volume at 20° C. The timewhich was required for the primer coating to peel 2 mm from the cut endof the polyolefin material was measured. A required time of more than 30minutes was regarded as passing the test.

-   4. Resistance to high-pressure washing

The polyolefin materials were cut to form slashes by a cutter knife forlengths of 7 cm until the blade reached the material under the coatingsand fixed horizontally, and high-pressure water at 20° C., pressure 70kg/cm² was blown from an angle of 30°, from a distance of 20 cm for 30seconds. The length of peeled primer coating from the polyolefinmaterial was measured. Pieces in which peeling did not occur wereregarded as passing the test.

-   C. Results of evaluation

As is obvious from Tables 3 and 4, Examples 1 to 6 exhibited superiorperformance in adherence, moisture resistance, gasohol resistance, andresistance to high-pressure washing. However, in Comparative Example 1,in spite of high content of acrylic resin polymer component in acrylicdenatured alkyd resin, resistance to high-pressure washing was inferiorbecause the ratio of acrylic denatured alkyd resin was low. InComparative Example 2, in spite of high content of alkyd resin polymercomponent in acrylic denatured alkyd resin, adherence, moistureresistance, gasohol resistance and resistance to high-pressure washingwere inferior because the ratio of acid anhydride denatured chlorinatedpolyolefin was low. Furthermore, in Comparative Example 3, though therewas no problem in the ratio of acid anhydride denatured chlorinatedpolyolefin and acrylic denatured alkyd resin, resistance tohigh-pressure washing was inferior because the glass-transitiontemperature of the acrylic resin polymer part was low. Furthermore, inComparative Example 4, resistance to high-pressure washing was inferiorbecause the molecular weight of the acrylic denatured alkyd resin waslow.

As explained so far, the primer composition for polyolefin material ofthe present invention can exhibit sufficient adherence, resistance tohigh-pressure washing, and gasohol resistance to polyolefin material byusing component A: acid anhydride denatured chlorinated polyolefin andComponent B: acrylic denatured alkyd resin in a content ratio of from80/20 to 20/80. Therefore, the primer composition for polyolefinmaterials of the present invention is extremely effective as a primerfor polyolefin material for exterior parts for an automobile.

1. A primer composition for polyolefin material, the primer compositioncomprising: a component A comprising acid anhydride modified chlorinatedpolyolefin consisting of propylene-α-olefin including at least one kindof α-olefin whose carbon number is 2 or 4 or 5 or 6; a propylene contentof 50 to 99 mol %; a chlorine content of 15 to 24% by weight; an acidanhydride content of 0.6 to 2.0% by weight; and a weight averagemolecular weight of 40000 to 120000; and a component B comprisingacrylic modified alkyd resin in which alkyd resin polymer part (b1)whose iodine value is 80 or more and oil length is 35 to 70%, andacrylic resin polymer part (b2) whose glass-transition temperature isnot less than 50° C., wherein the weight average molecular weight is10000 to 100000, and a weight ratio of b1/b2 is 25/75 to 75/25; whereina weight ratio of the component A and the component B is 80/20 to 20/80.2. A method for production of a primer composition for polyolefinmaterial including acid anhydride modified chlorinated polyolefin andacrylic modified alkyd resin, the method comprising: obtaining acidanhydride modified chlorinated polyolefin by copolymerizing propyleneand α-olefin, conducting chlorination of this propylene-α-olefincopolymer, and conducting addition reaction by adding acid anhydride;obtaining acrylic modified alkyd resin by conducting alcoholysisreaction of oil and polyhydric alcohol, performing esterification byusing a polybasic acid, and conducting acrylic modification by addingacrylic monomer and peroxide; and mixing acid anhydride modifiedchlorinated polyolefin, acrylic modified alkyd resin, and organicsolvent, so as to obtain a coating.
 3. The method for production of aprimer composition for polyolefin material according to claim 2, whereinthe primer composition for polyolefin material is colored by applying apigment.
 4. The method for production of a primer composition forpolyolefin material according to claim 2, wherein the primer compositionfor polyolefin material is prepared to be conductive by coating materialfor electrostatic coating.